During the scene where Etta James is singing "I'd Rather Go Blind", she is seen with the microphone in her hand at the beginning of the second verse of the song. The camera then shows her from behind so Adrien Brody's character can be seen exiting the studio and the microphone can be seen clearly over her shoulder still on its stand. A second later the camera cuts to her face again and she is somehow still holding the microphone.
Little Walter died at his girlfriend's home, not at Muddy Waters' home, and not in the arms of Muddy's wife.
Etta James is portrayed as never having recorded before she signed with Chess, but an earlier insert shot showing a Chess record moving up the charts includes her hit "Wallflower," recorded for Modern Records in 1955, five years before she started recording for Chess.
Every time a 45 rpm record is shown being played in the movie, it is actually rotating at 78 rpm.
Etta James and Minnesota Fats are shown meeting in the early 1960s. According to James' autobiography, the two did not meet until 1987.
Muddy Waters would not have been able to cross the hands of dead Little Walter's as easily as he did. By the time Little Walter had been dressed and placed in the casket his arms would have been too stiff to move that easy.
When Leonard Chess drives away from the studio for the last time, he looks into the rear-view mirror. The Chess sign should be reversed, but it isn't.
When Muddy Waters crosses the hands of dead Little Walter, Walter's thumb moves slightly.
When the animated sequence shows "Maybelline" breaking into the pop charts and climbing up to number 5, the number 4 hit "Love Is A Many Splendored Thing" is misspelled "Spendored".
Everyone at Chess Records drives a '57 Cadillac, in 1955.
In the film, Leonard Chess dies, then Muddy Waters and Willie Dixon go to Europe to perform in 1967. Leonard Chess died October 16, 1969.
Chuck Berry is depicted as angrily pointing out the resemblance between the Beach Boys' "Surfin' U.S.A." and his own "Sweet Little Sixteen" at the time of his arrest for violating the Mann Act. Berry was in fact arrested on this charge in December 1959, and ultimately (after two trials and a failed appeal) sent to prison from February 1962 to October 1963. "Surfin' U.S.A." was released in March 1963, when Berry was still in prison.
In the film, Leonard Chess opens Chess Studios in 1954 or 1955. It actually opened in 1957. Before that, Chess recorded exclusively at Universal Recording.
The 45 RPM record was not widely used during the time the film was set. Until the late 1950s, 78 RPM records were the state-of-the-art at home and on the radio. Studios were pressing mostly 78's when Chess Records started, but they don't appear anywhere in the film.